After finishing the layout I aksed for some review by PCB experts/enthusiasts Reddit. A nice and interesting discussion followed and made me redesign some things: via annular rings, position of decoupling capacitors, repour of gnd planes etc. I'm going to give it a double check once again and send it to fabrication to OSH Park before the weekend.

P.S. I've uploaded the new screen shots in "Files" section, but Hackaday.io keeps the old screenshots for some reason. Maybe because of the same filename?